1. Field of the Invention
The present invention relates to an antenna, and more particularly to a multi-frequency antenna, which integrates several operating frequency bands therein.
2. Descriptions of the Related Art
With fast progress of wireless communication technology, RF channels become more and more crowded. Wireless communication technology has expanded from dual-band systems to triple-band or even quad-band systems. In 2007, the industry of notebook computer's antenna has a bigger change: The wireless communication begins to enter the 3G or 3.5G age after the Centrino chip had pushed maturation of built-in WLAN. Thus, the number of the built-in antennae also increases. The current notebook computers are mainly equipped with built-in antennae. In the Centrino age, there are only two built-in antennae. In the 3G age, there may be 5-6 built-in antennae. The additional antennae include an 802.11n MIMO antenna, two 3G antennae, and even one or two UWB antennae. Such dual-band antenna is for example disclosed in U.S. Pat. No. 7,466,272 B1. Usually, a multi-frequency antenna is integrally made by cutting and bending a metal sheet to form a three-dimensional structure. Further, in a quad-band antenna with two coaxial cables, one coaxial cable feeds signal to both a first and second antennas, and the other feeds signal to both a third and fourth antennas, such as the structure taught in U.S. Pat. No. 7,289,071 B2.
After notebook computers joined the mobile communication industry, the manufacturers have to propose a sophisticated antenna design and a superior RF system implementation tactic, in addition to a standard 3G communication module, so that the notebook computers can transceive signals accurately and noiselessly in a communication environment full of interference. Further, a notebook computer involves many communication systems, such as GPS, BT, Wi-Fi, WiMax, 3G/LTE and DIV. How to achieve an optimized design compatible to these wireless communication systems has been a critical technology in the field. The customers have a very high requirement for the compactness and slimness of notebook computers. How to integrate more and more antenna modules into smaller and smaller space without mutual interference becomes a big challenge for designers.